Is it possible to tell whether people are truly happy just from their laugh?

A researcher from Royal Holloway, University of London, contends that there are clear differences between how people's brains responds to genuine and fake laughter.

"It's fascinating to consider the way our brain is able to detect genuine happiness in other people," Dr. Carolyn McGettigan said in a statement. "Our brains are very sensitive to the social and emotional significance of laughter."

For the study, McGettigan recorded the brain responses of participants as they listened to the same people produce genuine laughter, caused by watching funny YouTube videos, and forced laughter.

The participants, who were unaware the study was about laughter perception, demonstrated different neurological responses when they heard false laughter. McGettigan said this suggested that human brains not only distinguish between the two types of laughter, but attempt to work out why the fake laughter is not genuine.

"During our study, when participants heard a laugh that was posed, they activated regions of the brain associated with mentalizing in an attempt to understand the other person's emotional and mental state," she said.

She added that some participants engaged parts of the brain that control movements and detect sensation.

"These individuals were more accurate at telling which of the laughs were posed, and which were real," McGettigan said. "This suggests that as listeners, 'trying out' how a laugh would feel if we produced it ourselves might be a useful mechanism for understanding its meaning."